Vulcanizable rubber composition and process for vulcanizing same



VULCANIZABLE RUBBER COMPOSITION AND PROCESS FOR VUL'CANIZING SAME David James Bryans Coulter and Vincent Kerrigan, Man-V chester, England, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain r 1 v No Drawing. Filed Feb. 4, 1957, Ser. No. 637,860

' Claims priority, application Great Britain Jan. 30, 1951 7 Claims. (Cl. 260-415) This invention relates to an improved vulcanization process for rubber, and more particularly it relates to an improved vulcanization process for rubber stocks containing a reinforcing type furnace black.

The incorporation of a furnace black in rubber tends.

to cause the resultant rubber stock to scorch during processing. This tendency to scorch cannot be efiectively controlled by the-addition of all substances which are effective scorch-inhibitors in gum and channel black stocks. Also some substances which are efiective retarders in furnace black stocks are subject to certain disadvantages. p

Thus, for example, the tendency to scorch can be reduced by incorporating in the rubber stock a nitrosamine, for example N-nitrosodiphenylamine or N-nitroso-2:2:4-, trimethyl-l:Z-dihydroquinoline but there is a tendency for retarders of this type to produce under certain circumstances a porous vulcanizatc.

We have now found that vulcanizable rubber compositions particularly those containing a reinforcing type furnace black can .be processed'with. a high margin of safety, possess a reduced tendency to scorch, and produce a non-porous vulcanizate, when there is incorporated therein an "accelerator and sulphamic acid and/or certain derivatives thereof;

i Thus "according to our invention we. provide an im proved process for the vulcanization of rubber characterised in that there is incorporated therein a vulcanizing agent and an accelerator and asubstance of the formula:

- R [R 'NS0 "X],,

wherein n stands for 1 are "and wherein R stands for a hydrocarbon radicahoptionally substituted, or, when n is 1, for hydrogen or for a hydrocarbon radical, optionally substituted, R stands for hydrogen or for a hydrocarbon radical, optionally substituted, and when n is 1, R and R together may form, together with the adjacent nitrogen atom, part of a hete'rocyclic-ring, and wherein pholine, l:4-bis(dimethylsulphamyl) piperazine, zincsulphamate,-

s ulphamate calcium sulphamate,

magnesium sulphamate, aluminium sulphamate, 2:4-di-- chlorophenyl dimethylsulphamate, p-cyclohexylphenyl dimethylsulphamate and cyclohexylsulphamic acid; It is preferred to use Sulphamic acid or its salts.

The amount of the said substance which may be added may be up to 3% and is preferably not more than 1.0% on the rubber hydrocarbon.

The. processof. the present invention is particularly suitable for the vulcanization of rubber stocks contain ing a reinforcing type furnace black. The term rein- 2,945,834 Patented July 19, 1960 forcing type furnace black is used in a broad sense to mean furnace blacks more reinforcing in effect than mere diluents and includes semi-reinforcing furnace blacks and high reinforcing furnace blacks, for example those referred to in the trade as fine furnace black, high modulus furnace black, medium abrasion furnace black, high abrasion furnace black, and super abrasion [furnace black.

As accelerators which may be incorporated in the rubber in the process of our invention there are preferably used delayed action accelerators for example those delayed action accelerators of the sulphenamide type or those containing a 'thiazole nucleus. mentioned as suitable accelerators thiazole sulphenamides prepared from amines containing alkyl, especially tertiary alkyl or'cycloalkyl, or heterocyclic radicals such as N- tert. butylbenzthiazylsulphenamide, N tert. octylbenzthiazylsulphenamide, N-cyclohexylbenzthi'azyl sulphenamide, benzthiazyl sulphenmorpholide and benzthiazyl sulphenpiperidide; also mercaptobenzthiazoles wherein the hydrogen of the mercapto group is substituted by an organic radical, such as 2:4-dinitrophenyl-2-benzthiazyl monosulphide, ethylbenzthiazyl disulphide, and 2:2'-dibenzthiazyl disulphide and guanidine derivatives for example diphenylguanidine and di-o -tolylguanidine. The accelerator may for example be used in quantities up to 2% on the rubber hydrocarbon.

' thetic rubber for example polymers of butadiene-1z3 and 2-methylbutadiene-lz3, and, copolymers of these compounds with acrylonitrile, styrene, methyl methacrylate and. other well known polymerisable compounds used in the, manufacture of these rubbers. As used in the claims, the term polymers includes such copolymers.

"The rubber may also contain, incorporated therein, other known adjuvants, for example zinc oxide, pigments, antioxidants, peptisers and softeners. V

The vulcanization of the rubber may be carried out under conditions known in the art, for example by heating 'attemperatures between 130- C. and 150 C. for example 30 to 60 minutes. a 7

.Rubber containing a reinforcing. type furnace black when vulcanized by the process of our invention possesses excellent and uniform physical properties, and the unvulcanized stocks may be processed with a high degree of safety, as shown, for example by the scorching times at 110 C., as measured on a Mooney Plastometer.

, These scorching times are increased by as much as by 45% as compared with a mix containing none of the substances as hereinbefore' defined. White base stocks vulcanized by the process of our invention produce a non-stained, non-porous'vulcanizate.

The invention is illustrated but, not limited by the following examples in which the parts are by weight:

7 EXAMPLE 1 V V A rubber stock is made, upfrom the following ingredients: r a V Parts Smoked sheet rubber 100 Zince oxide I g 5 Philblack 0 furnaceblack 47.5 Stearic acid V a .3. Sulphur 2.5.-, N-cyclohexylbenzthiazylsulphenamide 0.65 Sulphamic acid j 0.5

This rubberstock is submitted to the Mooney scorching Thus there may be 3 of 64 minutes. A rubber stock made up from the same proportions of the same ingredients, but omitting the sulphamic acid, is found to show a scorching time of 44 minutes in the Mooney scorching test at 110 C.

EXAMPLE 2 A rubber stock made up as described in Example 1, but substituting 0.5 part of 4:4-sulphonyldimorpholine for the 0.5 part of sulphamic acid, is found to show a scorching time of 51 minutes in the Mooney scorching test at 110 C.

- EXAMPLE 3 A rubber stock made up as described in Example 1 but substituting 0.5 part of zinc sulphamate for the 0.5 part of sulphamic acid, is found to show a scorching time of 60 minutes in the Mooney scorching test at 110 C.

EXAMPLE 5 A rubber stock made up as described in Example 1 but substituting 0.5 part of 2:4-dich1orophenyldimethy1- sulphamate for the 0.5 part of sulphamic acid, is found to have a scorching time of 53 minutes in the Mooney scorching test at 110 C.

The 2:4-dichlorophenyldimethylsulphamate used in the process of the above example is a new compound and may be obtained by the action of dimethylaminosulphonyl chloride on 2:4-dichlorophenol in the presence of an acid-binding agent.

EXAMPLE 6 A rubber stock made up as described in Example 1, but substituting 0.5 part of p-cyclohexylphenyl dimethylsulphamate for the 0.5 part of sulphamic acid, is found to show a scorching time of 53 minutes in the Mooney scorching test at 110 C. a a

The p-cyclohexylphenyl dimethylsulphamate used in the process of the above example is a new compound and may be obtained by the action of dimethyl aminosul phonyl chloride on p-cyclohexylphenol in the presence of an acid-binding agent.

EXAMPLE 7 A rubber stock made up as described in Example 1, but substituting 0.5 part of calcium sulphamate for the 0.5 part of sulphamic acid, is found to show a; scorching time of 60 minutes.

EXAMPLE 8 A rubber stock made up as described in Example 1, but substituting 0.5 part of magnesium sulphamate for the 0.5 part of sulphamic acid is found to show a scorching time of 62 minutes.

EXAMPLE 9 A rubber stock made up as described in Example-1, but substituting 0.5 part of aluminium sulphamate for the 0.5 part of sulphamic acid is found to show a scorching time of 59 minutes.

EXAMPLE 10 A rubber stock made up as described in Examplel,

but substituting 0.5 part of sodium sulphamate for the .4 0.5 part of sulphamic acid is found time of 53 minutes.

to show a scorching EXAMPLE 11 Furnace black tread compounds are made up from the following ingredients:

These compounds are submitted to the Mooney Scorching Test at C., and the following results are obtained:

A B O Plasticity after 4 minutes... 96 9s 98. Time to reach Mooney value 32 minutes. 38 minutes 45 minutes.

10 units above minimum. Time to reach Mooney value 33 minutes. 39 minutes 46 minutes.

20 units above minimum.

EXAMPLE 12 Furnace black tread compounds are made up from the following ingredients:

Smoked sheet 100 100 Zinc oxide 5 5 Kosmos 60 High Abrasion Furnace Black 47. 5 47. 5 Stearie Acid 3 3 Sulphur 2. 5 2. 5 Mercaptoben 1i'hia7nle 0. 65 0. 65 sulphamic acid 0. 5

These compounds are submitted to the Mooney scorching test at C., and the following results are obtained:

.These stocks are submitted to the Mooney Scorching Test at 120 C., and the following results are obtained:

Plastieit after4minutes .L 47 47 Time to reaeh Mooney value 10 units aboveminimum .00 14minutes.. Minutes.

11 M one value a l; v e rn i n irn 111111-0 16 minutes 21 minutes.

EXAMPLE 14 Rubber stocks are made up from the following ingredients:

Pale crepe 100 100 Zinc oxide... 10 Blane fixe... 75 75 Stearic acid. 1 1 1O Sulphur 2.5 2.5 Mercaptobenzt azole ..l 0.5 0.5 Sulphaniic acid 0. 3

The stocks are submitted to the Mooney Scorching Test at 120 C., and the following results are obtained:

Plasticity after4 minutes 47 44. Time to reach Mooney value 10 units above minimum 13 minutes. 21 minutes. Time to reach Mooney value 100 18 minutes. 30 minutes.

EXAMPLE 15 25 Cable insulation compounds are made up from the following ingredients:

Smoked sheet 100 100 Zine oxide 5 5 Tale 50 50 China clay (Kaolin). 5O 50 Parafiinwax 3 3 Stearic acid 1 1 Acetone (Diphenylamine condensate)- 1 1 Sulphur 1. 25 1. 25 Mereaptobenzthiazole 1. 125 1. 125 Zinc diethyldithio carbamate. 0. 375 0. 375 Sulphamic acid 0. 5

The compounds have the following properties:

Press cured-15 seconds at 198 C.

MOONEY SCOROHING AT 120 C. Plasticity after 4 minutes 48 50. Time to reach Mooney value 10 units above minimum 8 minutes 14 minutes. Time to reach Mooney value 100 9 minutes. 17 minutes. Volume Resistivity at 20 0. (ohm. cm.)

EXAMPLE 16 Rubber stocks are made up from the following ingredients:

M N P Polysar Krylene (GR-S) 100 100 100 Zine oxide 5 5 5 Btearic acid 3 3 3 Kosmos 85 Super Abrasion Furnace Black.-. 47. 5 47. 5 47. 5 Sulphur 2 2 2 N-cyclohexylbenzthiazyl sulphenamide 5 1.5 1.5 Sulfamic acid 0. 5 1

Physical test results Property Cure M N P;

min. 15 267 260 228 Tensile strength (kg/sq. cm.) 20 277 265 256 30 256 222 263 45 232 244 237 15 166 126 96 Modulus 300% (kg/sq. em) 20 213 178 150 30 224 198 173 g 45 236 210 192 15 443 495 533 Elongation at break (percent) 20 392 419 456 30 358 358 421 :2 r 2 Hardness (BS) 20 76 75 30 77 76 74 45 77 75 74 15 43 40 37 Resilience 50 0. (percent) 20 43 42 41 30 45 43 42 45 43 43 43 Mooney Scorchmg Test at 120 C.

M N P Plasticity after 4 minutes 53 54 53 Time to reach Mooney value 10 units above minimum (minutes) 45 Time to reach Mooney value 20 units above minimum (minutes) 48 Time to reach Mooney value (minutes) 52 75 75 What we claim is:

1. A process for vulcanizing a rubbery polymer of a monomer selected from the group consisting of butadiene- 1:3 and 2-methyl butadiene-1:3 which comprises heating said polymer at a vulcanizing temperature in the presence of between about 1 and about 3 percent of a rubber vulcanizing agent, up to about 2 percent of a rubber vulcanizing accelerator containing the thiazole nucleus and between about 0.2 and 3 percent of a compound selected from the group consisting of sulphamicacid, salts of sulphamic acid, 4:4-sulphonyldimorpholine, 1:4-bis (dimethylsulphamyl) piperazine, 2:4-dichlorophenyl dimethylsulphamate, p-cyclohexylphenyl dimethylsulphamate and cyclohexyl sulphamic acid.

2. A process for vulcanizing as set forth in claim 1 in which said compound is sulphamic acid.

3. A process for vulcanizing as set forth in claim 1 in which said compound is 4:4-su1fonyldimorpholine.

4. A process for vulcanizing as set forth in claim 1 in which said compound is 1:4-bis-(dimethylsulfonyl) piperazme.

5. A process for vulcanizing as set forth in claim 1 in which said rubbery polymer contains reinforcing furnace black.

6. A process for vulcanizing as set forth in claim 1 in which said vulcanizing agent is sulfur.

7. A vulcanizable rubber composition consisting essen tially of a rubbery polymer of a monomer selected from the group consisting of butadiene-1:3 and Z-methyl butadiene-l :3, between about 1 and about 3 percent of a rubber vulcanizing agent, up to about 2 percent of a rubber vulcanizing accelerator containing the thiazole nucleus and between about 0.2 and 3 percent of a compound selected from the group consisting of sulphamic acid, salts of sulphamic acid, 4:4-sulphonyldimorpholine, 1:4-bis (dimethylsulphamyl) piperazine, 2:4-dichlorophenyl dimethylsulphaniate, p-cyclohexylphenyl dimethylsulphamate and cyclohexyl sulphamic acid.

2,704,761 DAmico Mar. 22, 1955 

1. A PROCESS FOR VULCANIZING A RUBBERY POLYMER OF A MONOMER SELECTED FROM THE GROUP CONSISTING OF BUTADIENE1:3 AND 2-METHYL BUTADIENE-1:3 WHICH COMPRISES HEATING SAID POLYMER AT A VULCANIZILNG TEMPERATURE IN THE PRESENCE OF BETWEEN ABOUT 1 AND ABOUT 3 PERCENT OF A RUBBER VULCANIZING AGENT, UP TO ABOUT 2 PERCENT OF A RUBBER VULCANIZING ACCELERATOR CONTAINING THE THIAZOLE NUCLEUS AND BETWEEN ABOUT 0.2 AND 3 PERCENT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF SULPHAMIC ACID, SALTS OF SULPHAMIC ACID, 4:4-SULPHONYLDIMORPHOLINE, 1:4-BIS (DIMETHYLSULPHAMYL) PIPERAZINE, 2:4-DICHLOROPHENYL DIMETHYLSULPHAMATE, P-CYCLOHEXYLPHENYL DIMETHYLSULPHAMATE AND CYCLOHEXYL SULPHAMIC ACID. 